Optical characterization of a neodymium-doped lithium-niobate-on-insulator (LNOI)

Abstract

A neodymium (Nd) doped lithium-niobate-on-insulator (LNOI) was fabricated from a lithium niobate (LN) substrate diffusion-doped with Nd prior to the LNOI fabrication process. Diffusion doping enables the fabrication of differently doped regions on a single LNOI substrate, a key advantage for future applications in highly integrated photonics. Fluorescence spectra, emission cross-section, fluorescence lifetime, and small-signal gain of Nd:LNOI were determined for the first time to our knowledge and compared with data published for diffusion-doped ridge or channel waveguides in LN substrates. For an 11 mm-long sample, we achieve a small-signal gain for π (σ) polarization of about 14 (10) dB when pumping with a Ti:Sapphire laser, which is promising for future active components in Nd:LNOI like amplifiers and lasers.